ALLOCATE CHANNEL

To manually allocate a channel, which is a connection between RMAN and a database instance. Each connection initiates an database server session on the target or auxiliary instance: this server session performs the work of backing up, restoring, or recovering RMAN backups.

Manually allocated channels (allocated by using ALLOCATE) should be distinguished from automatically allocated channels (specified by using CONFIGURE). Manually allocated channels apply only to the RUN job in which you issue the command. Automatic channels apply to any RMAN job in which you do not manually allocate channels. You can always override automatic channel configurations by manually allocating channels within a RUN command.

Each channel operates on one backup set or image copy at a time. RMAN automatically releases the channel at the end of the job.

You can control the degree of parallelism within a job by allocating the desired number of channels. Allocating multiple channels simultaneously allows a single job to read or write multiple backup sets or disk copies in parallel. If you establish multiple connections, then each connection operates on a separate backup set or disk copy.

Whether ALLOCATECHANNEL causes operating system resources to be allocated immediately depends on the operating system. On some platforms, operating system resources are allocated at the time the command is issued. On other platforms, operating system resources are not allocated until you open a file for reading or writing.

Note:

When you specify DEVICETYPEDISK, no operating system resources are allocated other than for the creation of the server session.

You cannot use BACKUPDEVICETYPE or RESTOREDEVICETYPE to use automatic channels after specifying manual channels with ALLOCATECHANNEL.

You must use a recovery catalog when backing up a standby database.

You cannot prefix ORA_ to a channel name. RMAN reserves channel names beginning with the ORA_ prefix for its own use.

Keywords and Parameters

Syntax Element

Description

AUXILIARY

Specifies a connection between RMAN and an auxiliary database instance. An auxiliary instance is used when executing the DUPLICATE or TRANSPORTTABLESPACE command, and when performing TSPITR with RECOVERTABLESPACE. An auxiliary database can reside on the same host as its parent or on a different host. When specifying this option, the auxiliary database must be mounted but not open.

See Also:"DUPLICATE" to learn how to duplicate a database, and "CONNECT" to learn how to connect to a duplicate database

CHANNEL'channel_id'

Specifies a connection between RMAN and the target database instance. Each connection initiates a server session on the database instance: this server session performs the work of backing up, restoring, and recovering backups and copies.

Specify a channel id, which is the case-sensitive name of the channel, after the CHANNEL keyword. The database uses the channel_id to report I/O errors.

Note: If you do not specify the DEVICETYPE parameter, then you must specify the NAME parameter to identify a particular sequential I/O device. Query the V$BACKUP_DEVICE view for information about available device types and names.

Spreading a Backup Across Multiple Disks: Example When backing up to disk, you can spread the backup across several disk drives. Allocate one DEVICETYPEDISK channel for each disk drive and specify the format string so that the filenames are on different disks:

Creating Multiple Copies of a Backup: Example When creating multiple copies of a backup, you can specify the SETBACKUP COPIES command. The following example generates a single backup of the database to disk, and then creates two identical backups of datafile 1 to two different file systems: